The present invention relates to a method for determining a target curve incline of a motor vehicle during travelling of a curved roadway section, as well as a device to determine a curved incline of a motor vehicle during travelling of a curved roadway section. The invention furthermore relates to a motor vehicle having such a device.
Electro-hydraulically active chassis systems are known by the term “Active Body Control (ABC)”, which, besides a conventional spring and dampener function, also allow the possibility of the targeted setting of pitch and roll angles. A roll is therein referred to as a rotational movement of a motor vehicle around its longitudinal axis. Such a roll movement can result during travelling of a curved roadway section by the motor vehicle if the motor vehicle inclines outwards around a determined roll angle due to the occurring centrifugal forces. The roll angle set here depends on the transverse acceleration of the motor vehicle, the center of gravity height, the chassis construction of the motor vehicle as well as the speed thereof.
The centrifugal forces occurring during travelling of the curved roadway section are often uncomfortable to experience for the passengers of the motor vehicle and can therefore lead to a considerable reduction of the driving comfort. A possibility to reduce the comfort-reducing effect of such undesired transverse forces on the passenger of the motor vehicle consists in implementing incline technology in the motor vehicle by means of “Active Body Control (ABC)”, as has already been used for a long time in rail vehicles. By using such incline technology, it is possible for the motor or rail vehicle not to incline outwards during travelling of a curved roadway or rail section, but rather in the opposite direction, so inwards, due to corresponding control of a chassis of the motor vehicle. For this purpose, the chassis can be provided with suitable actuators, for example in the manner of height-adjustable struts which connect the vehicle frame to each wheel of the motor vehicle in a height-adjustable manner, such that a determined roll angle of the motor vehicle can be set.
As the centrifugal forces occurring during travelling of the curved roadway section depend on different factors, such as for example a roadway curvature of the roadway section or the momentary speed, the roll angle to be set in the sense of incline technology on the chassis of the motor vehicle must also be determined depending on these parameters in order to ensure as high a level of driving comfort as possible for the passengers.
DE 10 2010 046 317 A1 describes a method to set the spatial position of a roll axis around which the motor vehicle is able to rotate at a predetermined roll angle. According to the method, firstly in a first step, a spatial target position of the position of the roll axis is set and subsequently in a second step, a transverse acceleration of the motor vehicle is determined. In a third step, a target cross slope of the motor vehicle and target transverse offset of the motor vehicle is finally determined depending on the transverse acceleration, such that when setting the target cross slope and the target transverse offset, a transfer of the roll axis into the target position is caused. In order to ensure that the motor vehicle occupies the target cross slope determined in the previous step, at least one actuator of an active chassis device of the motor vehicle is adjusted accordingly. Additionally, at least one actuator to influence the transverse movement of the motor vehicle is adjusted in such a way that the motor vehicle additionally also occupies the target transverse offset determined in the previous step. The expected transverse acceleration can, for example, be determined with the aid of a camera system attached to the motor vehicle, which optically detects the curved roadway section in front of the motor vehicle which is to be travelled and analyses it to determine the expected transverse acceleration.
DE 10 2006 018 978 A1 describes a method for determining a roll angle of a motor vehicle having at least one device to determine the yaw rate or a value correlated thereto as well as a device for determining the vehicle speed and a camera system which is possibly directed forwards. The roll angle is determined by using the yaw rate or a value correlated thereto and the specific roll spring stiffness of the vehicle.
It is the object of the present invention to specify an improved embodiment for a method for determining a target curve incline (=roll angle) of a motor vehicle during travelling of a curved roadway section as well as a device for determining this target curve incline.
The invention is based on the general idea to calculate the target curve incline to be determined based on a momentary roadway curvature determined by means of an optical detection system, wherein the determination of the momentary roadway curvature additionally occurs by using a vehicle navigation system of the motor vehicle. For this purpose, the information with regard to the roadway curvature of the respective roadway section contained in the map data can be gleaned.
In addition to the sensor output data provided by the optical detection system, map data of the vehicle navigation system can therefore be used for the calculation of the roadway curvature. A great advantage of the use of such map data consists in that the roadway curvature can be determined not only during travelling of a determined roadway section, but can be determined by corresponding reading of the map data for any roadway section of the map data stored in the vehicle navigation system. Additionally, such map data often contains further map information such as, for example, a longitudinal incline and—if present—also a cross slope of the roadway section. As the map data of the vehicle navigation system is alone not sufficient for the determination of the roadway curvature in a practical operation of the motor vehicle (as the map data, for example, can be outdated due to constructional changes of the course of the road), the determination of the momentary roadway curvature using the vehicle navigation system occurs, according to the invention, only as a support for the actual determination of the roadway curvature by means of the optical detection system which, for example, can be a camera system which provides an image of what is in front of the motor vehicle as sensor output data.
In this context, it is particularly conceivable that the momentary roadway curvature determined by means of the vehicle navigation system is used for verification of the roadway curvature determined by means of the optical detection system. It can also be conceived that, with the aid of the vehicle navigation system, values of the momentary roadway curvature which are determined by means of the optical detection system and which contain errors can be corrected.
Due to the extraction of the roadway curvature from the map data of the vehicle navigation system according to the invention, it is therefore possible to filter out different types of disturbances such as a road displacement or a determined steering behavior of the driver of the motor vehicle from the sensor signals of the optical detection system.
From the momentary roadway curvature determined by means of the optical detection system in connection with the vehicle navigation system, a momentary transverse acceleration of the motor vehicle can be determined by means of the method according to the invention and from this, the desired target curve incline can be determined, wherein this is weighted with a speed-dependent weighting factor. Thus, by means of the method according to the invention, an optimum target curve incline (=roll angle) for the travelling of a curved roadway section can be determined, which, if it is set by means of an adjustable chassis of the motor vehicle, leads to improved driving comfort for the passengers of the motor vehicle. By means of the weighting of the momentary target curve incline with a speed-dependent weighting factor, an optimized roll angle of the motor vehicle which is set in the chassis can be determined for the travelling of the curved roadway section, for which transverse forces acting on the vehicle passengers can be decreased particularly well or even can be almost completely eliminated, such that the driving comfort for the passengers of the motor vehicle can be clearly increased. Fundamentally, in the case of the application of the method according to the invention in a motor vehicle, the momentary transverse acceleration and the sought-after target curve incline derived therefrom can be determined for the motor vehicle with particularly high operational security.
In the method according to the invention, in a first step a), a momentary transverse acceleration of the motor vehicle can be determined depending on a momentary speed of the motor vehicle from a momentary roadway curvature of a curved roadway section determined by means of an optical detection system, wherein the determination of the momentary roadway curvature occurs according to step a) by using a vehicle navigation system of the motor vehicle.
In a second step b), a momentary target curve incline for the motor vehicle is determined from the momentary transverse acceleration calculated in step a). In a third step c), a modified momentary target curve incline is finally calculated by weighting the target curve incline calculated in step b) with a speed-dependent target curve incline weighting factor. Based on the modified target curve incline calculated in step c), a chassis of the motor vehicle can be controlled in such a way that the motor vehicle assumes the roll angle defined by the modified target curve incline relative to the road surface of the curved roadway section to be travelled. For this purpose, the chassis device can, for example, be provided with suitable height-adjustable actuators in the manner of struts.
In a preferred embodiment, the determination of the roadway curvature can occur by means of the vehicle navigation system by extraction of the roadway curvature from the map data of the vehicle navigation system allocated to the roadway section being travelled, wherein the allocation occurs by using a momentary position of the motor vehicle provided by a position sensor of the vehicle navigation system. In the course of such an extraction, the roadway curvature extracted from the map data is compared with the momentary roadway curvature determined by means of the optical detection system. It is also conceivable to use the momentary roadway curvature determined by means of the vehicle navigation system to verify the momentary roadway curvature determined by means of the optical detection system.
In a developing or alternative embodiment, a non-optical sensor system can be used in combination with the optical sensor system or, alternatively to this, to determine the momentary transverse acceleration. In the case of the use of a non-optical sensor system in combination with the optical detection system, the momentary roadway curvature determined by means of the vehicle navigation system can be used as explained above for supporting determination of the momentary roadway curvature by means of the optical detection system.
In the case that the momentary transverse acceleration of the motor vehicle is not determined by means of an optical detection system, however, the momentary transverse acceleration can be determined by means of the vehicle navigation system (by determination of the momentary roadway curvature instead of the determination by means of the optical detection system) in order to verify the momentary transverse acceleration determined by means of the non-optical sensor system. Thus the non-optical sensor system can, on the one hand, be used synergistically with the optical detection system or alternatively to this, and in both cases, the vehicle navigation system can be used for verification purposes. In this way, the momentary transverse acceleration can be determined particularly accurately.
Preferably, the non-optical sensor system comprises an acceleration sensor, in particular a g-sensor, which provides a momentary sensor transverse acceleration value as sensor output data.
Alternatively or additionally, the non-optical sensor system can comprise, in a particularly preferred embodiment, a yaw rate sensor, which provides a momentary yaw speed as sensor output data. The sensor output data present in the form of a momentary yaw speed can optionally be additionally filtered by means of a phase filter or/and a low-pass filter in order to be able to correct undesired disturbances in the sensor output data, for example due to unevenness in the surface of the roadway of the roadway to be travelled, among other things.
In a likewise preferred embodiment, the non-optical sensor system can comprise a steering wheel angle sensor or/and a wheel angle sensor which provides a momentary steering wheel angle or wheel angle of the steering wheel or of the wheels of the motor vehicle as sensor output data. For the determination of the momentary transverse acceleration from the steering wheel angle or wheel angle, for example, a simple one-track model can be used for the mathematical calculation. In more complex models allowing developed, more precise calculation results, the steering behavior or/and the tire running behavior of the motor vehicle can be included such that, in the case of such an overall consideration, the instructions of a driver of the motor vehicle can be particularly quickly and effectively implemented in the roll angle setting.
By means of the use of different types of sensor types in the non-optical sensor system (acceleration sensor, yaw rate sensor, steering wheel angle sensor, wheel angle sensor) to determine the momentary transverse acceleration, the sought-after target curve incline can be determined in an effective manner, independently of the actual lane information.
In developing embodiments, depending on different internal and external parameters, for example predetermined operational or/and error states of the non-optical sensor system or/and of the optical detection system, it can be also set in which manner the momentary roadway curvature or/and the momentary transverse acceleration are determined and whether the non-optical sensor system or/and the optical detection system is to be used here in combination with the vehicle navigation system or not.
According to the invention, to determine the momentary transverse acceleration, therefore, several of the sensor types referred to above of the non-optical sensor system combine with one another and are used together with the vehicle navigation system. The method according to the invention therefore offers, in terms of accuracy and operational reliability, a maximum level of flexibility for the determination of the momentary transverse acceleration and thus also for the calculation following this of the target curve incline of the motor vehicle.
The invention also relates to a device for the determination of a target curve incline of a motor vehicle during travelling of a curved roadway section. The device comprises an optical detection system by means of which a momentary roadway curvature of a momentary curved roadway section travelled by the motor vehicle is able to be determined. The device furthermore comprises a vehicle navigation system which comprises a data store having map data and a position sensor, and by means of which a momentary position of the motor vehicle is able to be determined. According to the invention, the control device determines the momentary roadway curvature of the curved roadway section by means of the optical detection system and in combination with the vehicle navigation system and from this a momentary target curve incline for the motor vehicle. From the momentary target curve incline, a modified target curve incline is calculated by weighting with a target curve incline weighting factor.
The invention furthermore relates to a motor vehicle having a device having the features referred to above as well as having a chassis device which is able to be controlled by the control device of this device, by means of which the modified target curve incline determined by the control device is able to be set in the motor vehicle.
Further important features and advantages of the invention result from the sub-claims, from the drawings and from the relevant description of the figures, by means of the drawings.
It is understood that the features referred to above and still to be explained below are not only able to be used in the respectively specified combination, but also in other combinations or alone, without leaving the scope of the present invention.
Preferred exemplary embodiments of the invention are depicted in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.